body {font-size: 14px;}
ul {list-style: none;}
.wrap {
    width: 100%;
    height: 100%;
    min-height: 100vh;
    overflow: hidden;
}

/**
icon 向下方向键,向上方向键
 */
p.demoSpan1{height:20px;}

p.demoSpan1:before{content:''; height:0; width:0; display:block; border:5px transparent solid; border-bottom-width:0; border-top-color:rgb(162,162,162); position:absolute; top:20px; right:5px;}
i.demoSpan1:before{content:''; height:0; width:0; display:block; border:5px transparent solid; border-bottom-width:0; border-top-color:rgb(68,68,68); position:absolute; top:15px; right:8px;}
i.demoSpan2:before{content:''; height:0; width:0; display:block; border:5px transparent solid; border-top-width:0; border-bottom-color:rgb(68,68,68); position:absolute; top:15px; right:8px;}

